Electric clutch transmission mechanism



March 16, 1954 R HELMER 2,672,565

ELECTRIC CLUTCH TRANSMISSION MECHANISM Filed April 7, 1950 4Sheets-Sheet l INVE NTOR ROBERT HELMER TMMiZ I am MT W BMUU ATTORNEYSMafch 16, 1954 R. HELMER ELECTRIC CLUTCH TRANSMISSION MECHANISM 4Sheets-Sheet 2 Filed April '7, 1950 'INVENTOR ROBERT HELMER ATTORNEYSMarch 16, 1954 HELMER 2,672,565

I ELECTRIC CLUTCH TRANSMISSION MECHANISM Filed April 7, 1950 4SheetsSheet 5 INVENTOR ROBERT 'HELMER BY fiwmzfa/mwamunm rBahnmmATTORNEYS Patented Mar. 16, 1954 IELEQTRICQCLUTCH TRANSMISSION MECHANISMRo-hert :HelmentGreat Neck,N. Y zassignor to i'flelmerTransmissioniflorporation, ta .c0rP01tation of Delaware ApplicationApril 7, 195 ,S erialNo.'4-,472

8 Claims. 1

This invention--'re1ates-to power transmission "mechanisms-Torconnecting: a :driving shaftto "a driven shaft, and more particuIarI-ytO mecha- =nisms "for" connecting the *-motor or "engine of amotor-vehicle to 'the driving wheels. The invention I aims to 'providean improved power transmission mechanism especiallyadapted' for use in amotor vehicle.

"Th1"oughout-this-specific ation'an-d the appended claims-the shaftconnected to 1 the source of power 'is called-the drivingsh-aft'and -the-shaft to be driven-thereby is oalled the driven *shaft.

The-power: transmission mechanism of the invention is-characterized by--a 'slippable coupling, preferably an electromagnetic coupling device,having two relatively rotatable members, a one I of which is connectedto the "driving shaft -and the other '01 =-which -is-rotatab1y mountedand connected*with a gear train which in turn-serves to -connect"thedriven shaft to the driving shaft. TreferabIy an auxiliary reversinggear 1 element engaging with the ggear train is provided f or re--versing"the direction or rotation of the -dri-ven shaft. Theelectromagnetic coupling deviceisadvantageously -in the 'natureofa-hysteresis -=cou- :pling; and-it is arranged'to alter the effectivegear ratio or the geartrain and so to change the torque *df the drivenshaft.

The 1, ,ear train is advantageously 'an *epicyclic 'geal" train, and inr such case is preferably of the type' having two sun gearsandaplanetary gear *train, withone of the sun gears connected'to the"driving shaft and I the other sun gear connected to one of'themembers'of the electromagnetic coupling device or other slippablecoupling. a.

"plingxe; g. the "magnetic orhys'teresis elementiof the hysteresis;coupling) is: connected to one sun gear of 'the'epicyclic; Withtheothersun gearjconnectedto the driving shaft. ,Theplanetaryzgear "trainiisoperativelyconnected to'the driven shaft,

preferablythrough a'rotatably mounted carrier etary gear train. Meansare provided :ior ibraking 'or -hoiding stationary :vboth :theirotata'bly mounted member (1. e. the member v:not secured to thedriving-sha'ft) of the-:geiectromagnetic (or *other *slippable) coupling-deviceandithe auxiliary reversing gear element.

-Ni hen .the :rotatably mounted memberi of ithe electromagnetic iievieeis free =ct0 rotateeunderct-he influence o'f its cooperatingmemberfithea-epicyclio gear-train connects the :driving and drivenshafts in high gear ratio, :and ivvhen the rotatably --mounted=memberOfitheelectrom'agnetio devioezis held stationary the epicycIiogea-rtrainrconnects the drivingand driveneshaf-ts in iowt-geareratio. Whenthetwo members Lofithe electromagnetic device rotate in: synchronism,the-:drivin-gsand driven-shafts are inefiec tadirect conneoted :(ime. agear ratio of 1:1), and the greater the relative speeds-ofthe tivomembers depart from synchronism, the 1 less is the speed: ofthedriveneshait relative to the driving shaf-t and theigreateriis theeffective-gear ratio oflthe: epicycl-ic geari train. The direction ofrotation of i the driven #s'haft is reversed by brak-ing or holdings'tationary the auxiliary reversing gear element.

The foregoing and other nOVe'I 'features of ime power 'transmissionmeohanism of the invention =-wi11 be best understood from-the*followingflescription and the -'-accompanying drawings, in which:

Fig. "1 is-a perspective view; partly in section, of one embodiment ofthe power transmission 'mechanisrn;

"Fig. 2 isa sectional elevation of the mechanism shown 'injFig. *1;

Figs3is a crosssectiontdzen-along=sectionline '3 3 of "Fig. i 2, =vvith'some of the outer gears brokenaway to show the inner gears;

'Fig. is--a -cross section taken- -along section line il 'o'i Fig.2

Fig. 5 is" a perspective "View; partly in section,

of the mechanism with amo'difiedbraking means *forjthe rotatabiemagneticmember;

.Eig. "6- is, 1 a *o1'oss 'section-of the mechani-smof Fig. 5, takensubstantially as indicated by the. ..seotion,line i 5 of Figgi5; and

Fig. '7 ".isga diagram of the electric circuits-Tor the. mechanismjnwhich the control "devices are diagrammatically indicated.

iReferring to; Fi s. "1! to ;4,' inclusive of 'the drawings, theoperative elements of the mechanism are supported within a casing,consisting of an outer cylindrical housing in having aninwardlyprojecting annular flange H to which is bolted a cylindrical capl2, and a plate l3 bolted to the front end of the housing. The plate |3carries a centrally positioned ball bearing I4 for the forward end of adriving jack shaft |5 which is splined or otherwise detachably connectedto the motor or other power source (not shown). The rear end of theshaft I5 is journaled at |6 in a. pilot bearing formed in a gear-carrierl1 having an integral output or driven shaft l3 rotatably carried by aball bearing |9 mounted in the rear end of the cap |2.

A spider 20 is keyed to the driving shaft I5, and has bolted to itsperiphery a plurality of circumferentially spaced electromagnetic polepieces 2|. One terminal of the coils 22 of the pole pieces (which coilsare advantageously connected together in series) is grounded and theother terminal is connected in any conventional manner to a slip ring 23suitably mounted on the shaft I5. A stationary brush 24 contacts theslip ring and electrically connects the coils 22 to the live orungrounded terminal of a low voltage source of electric energy, such asa generator or storage battery (Fig. 5)

A hard steel ring 25 which characteristically displays a high magnetichysteresis loss (hereinafter called a hysteresis ring) surrounds thepole pieces 2| in coaxial but suitably spaced relation thereto. The ring25 is rotatably mounted on the shaft I5, the ring being bolted between afront plate 26 with a cooperating ball bearing 21 (mounted on the shaftl5) and a rear plate 28 with a cooperating sleeve 29 journaled on theshaft I5. A lateral thrust bearing 30 is operatively mounted on theshaft |5 between the spider 20 and the sleeve 29. The rotatably mountedelectromagnetic pole pieces 2| and surrounding hysteresis ring 25 form aslippable hysteresis coupling.

A sun gear 3| (of an epicyclic gear train) is keyed to the rear end ofthe driving shaft l5. The sun gear 3| meshes with a cluster of threelong pinions or planet gears 32 rotatably mounted on circumferentiallyspaced shafts 33 mounted in the gear-carrier IT. The long pinions 32mesh with a cluster of three short pinions or planet gears 34 rotatablymounted on circumferentially spaced shafts 35 mounted in thegear-carrier H. The shafts 35 alternate circumferentially with theshafts 33, and all are arallel to each other and are concentricallydisposed about the axis of the shaft l5 (Fig. 3). The short pinions 34are positioned forwardly (i. e. to the left as viewed in Figs. 1 and 2)of the sun gear 3|. The pinions 32 are of sufficient length to mesh withboth the rearwardly mounted sun gear 3| and the forwardly mounted shortpinions 34. The short pinions 34 mesh with a forward sun gear 31rotatably mounted on the shaft |5 (adjacent to and forwardly of the rearsun gear 3|). The forward sun gear 31 is secured to the sleeve 29 bywhich the hysteresis ring is journaled and hence rotates therewith.

The gear-carrier I1 is a drum-like structure with its rear endintegrally secured to the driven shaft 3, and its forward end extendingradially beyond its cylindrical side H to provide an annular flange H",as best shown in Figs. 1, 2 and 6. The shafts 33 and 35 are mountedbetween the ends of the gear-carrier, and as the planet gears walk ortravel around the sun gears, their shafts travel similarly and rotatethe gear-carrier Hand attached driven shaft l8. A ring gear (or internalgear) 36, rotatably mounted on the cylindrical side l'l' of thegear-carrier, meshes with the short pinions 34. The pinions 34 are ofgreater diameter than the pinions 32 and extend through openings in theforward portion of the cylindrical side IT to permit engagement of thepinions with the ring gear 36. The ring gear is mounted for freerotation about the rear portion of the cylindrical side l1, and lateraldisplacement is prevented by the end cap l2 and the annular flange IT".

A brake band 46 surrounds the rear portion of the ring gear 36, and whentightened holds the gear ring stationary. When the gear ring is thusbraked or held stationary, the direction of travel of the planet gears32 and 34 about the sun gears is reversed, and hence the direction ofrotation of the gear-carrier l1 and the attached driven shaft H! arereversed. Any suitable mechanism (that shown in Fig. 3 comprises a pairof levers 41 supported on pivot pins 48 and having their upper armsjoined by pivotally connected toggle links 49 which may be pulled downwhen a solenoid 50 is energized) serves to set or tighten the brake band46, the brake band being normally loose and the ring gear free to rotatewith the gear-carrier.

In the form of apparatus shown in Figs. 1 and 2, the rear end of thesleeve 29 is threaded, and the threads engage the similarly-threadedbore of a conical brake plug, or clutch element, 33. The conical outersurface of the plug 38 is adapted to engage with and be held by thecorresponding conical inner surface of a stationary brake drum (ormating clutch element) 39 having an integral annular flange 39 boltedbetween the annular flange II and the cap I2 of the housing (Fig. 2).The forward end 39" of th drum 39 extends inwardly and carries a ballbearing 21 for supporting the sleeve 29. A coil compression spring 40normally biases the plug 33 and drum 39 to disengaged position, and theplug then freely rotates With the sleeve 29. A brake operating ring 4|is mounted on the peripheral edge of the annular flange 39' and isadaptedto be circumferentially moved through a small arc of travel. Theinner surface of the ring 4| has a plurality (three as shown in Fig. 4)of circumferentially spaced internal spiral cam faces 42 of graduallyincreasing depth. Pins 43 having a ball bearing contact 44 with the camfaces 42 extend through circumferentially spaced radial holes in theannular flange 39' and contact, at their inner ends, the periphery ofthe base of the brake plug 38. The ring 4| is adapted to be turned onthe flange 39' through a small arc (corresponding approximately to thearc subtended by one cam face 42) by an arm 45 secured thereto (Fig. 4)and connected to the plunger of a solenoid 45. Turning the ring 4|(clockwise in Fig. 4) by energizing the solenoid 45 forces the pins 43into engagement with the plug 38, thereby holding it stationary so thatsubsequent rotation of the hysteresis ring 25 will screw'the plug (tothe left in Fig. 2) along the threaded sleeve 29 into engagement withthe drum 39 and the hysteresis ring will then be held stationary.

The above-described mechanism functions as follows: When theelectromagnetic coils 22 are energized they create a magnetic fieldwhich permeates the hard steel hysteresis ring 25. Then when the coils22 are rotated by the shaft l5, the high hysteresis loss characteristicof the ring urges it to rotate with the coils. Assuming the hysteresisring thus to he rritating :at

same speed as the-coils time, withmo' 'slippmg of "the ring =relative-tothe rotating coils) -the rear-and forward sungears iil and 31respeeti-vly will beu otatingat the sam'e' speed. I'n

this rendition the train or planet gears 32, 34 must 'alsorotate-'with-the sun-gears; an'd at the same-speed,- becausec'fthedifference in diameter of the two sun gears. *Thus 'the qilanet gearcarrier *and thd'dli-VGIl-Shift- It attached toit rotate at the samespeed "as the sun -gears, and the driving and driven-shafts -are=in"effectdirectconnected; or in their *1:-1'-'-high gear ratio. If thereis'-some-="slipping =o'f 1 the -hysteresis ring 25 with *resp'ect-"tothe "rotatingwoiis 22 :e. if the hysteresis ring is' rotating moreslowlthan the' eoils) ,*as is the-'"casewhen a sudden loaii is ap'plied-to *the driven shaft 18j-then -the forward sunfigear t l will-rotatemore slowly than the rear sun 'gear 31, resultingin a reduetion inthe-speed with which the planet gear assembly *rotates a'round the sungears -and--a-corresp'onding reduction in "the speed of "rotation of=theilriven shaftN-B relative to that-Of the driving shaft' lli. At theextreme where the *load on "the driven shaft H3 holds this shaftstationary while 7 the driving shaft t5 (and hence the *reavsun gear 3+)is rctating-(as'when "the 'automob'ile is stationarywith the engineidling and-the hysteresis coilsde-energized), the planet gears willrotate on "their axes and-cause the forward sun gear 31, and thehysteresis'ring 2-5 connected "to it, to rotate in the directionopposite to that of the driving shaft 'ata 'speeddetermined by therelative diameters 'ofthevarious gears in the ep'icy'clic gear train.This condition -corresponds to maximum "slippagebetween the members(coils 22"an'd ring 25) *of the hysteresis-coupling.

"Theforegoing operation occurs-only when the brake -*plug *38 is out ofengagement with its mating brake drum 3'9 and 'when the hysteresis coilsare de-energized. Assume now that the coils '22 are-de-energized andthe'brake plug has been screwed into tight engagement with theStationary drum. *In thiscondition the hysteresis ring '25 'and-theforward sun gear "3-? i are restrained from rotating "at all. Thereforerotation of the rearsungear 3| bythe drivingshaft l5 -causes theplanetgears to walk around gear 31in 'the samedireetion as it (-31) rotates,but at a"reduc'ed speed-hecause the-forward sun-gear is stationary.Since the planet gears can now react against the forward sun gear, the"driven shaft 1 8 is enabled to deliver-an increased torque to "the loadconnected -to it. This condition (where the brake'plug -33 *and 'brakedrum 3'9 arein tight engagement) corresponds to; the low geariratio of"the 'transm'issionunit iin "Whichit can delivermaximumpower totheloa'd.

Inbothhighi'gear and tow gean'forward drives d8SCIibEd.&bOV8,'Zth(-lring gear 35' floats freely and "rotates in the 'same direction "as thesun gears. If the brake band 46 is tightenedtby energization of thesolenoid 50), the "ring gear is "restrained'from rotation, and 'with'therear sun gear-"31 being rritated-by the--"driving*shaft f5, -the planetgears are forced to Walkaround the rearsun.-gear ;in: a directionopposite --to its own: direction .101? rotation. This is :the reversegearreondition =;of;:the :transmission, in which "thedri'vsen:shaft;ziszrotated-ginithe oppositez'direetion t'o'lthezdrivingshaft. In thisacondition, oiaoourse, the; hysteresis ;coils3;2-2rare-:1-deeenergized andthe brake plug 38 is disengaged from the brake39. meverse-cgeaniithe :forward isun gear wand 6. the ihysteresis are:rotate'd rm ttne trever'ae direetiomto and at a higher-speed dzhanxthefiiivh1g shaftfiout since the'coils 2 2 "are not energized and the'brake or clutch unit 3'8, 39 =is4disengaged,

the hysteresis ring and forward 1 sun gearrotate a simple free ifloating==re1ation :to the driving shaft.

In the modification shown in Figs. *5 and 6 of='thedrawings; thehysteresis ringfli is mechanically *fiarake'd by ea brake i band 15'!adapted .to be- -set 'or itightened about the :hysteresi'sring' by atoggle llinkage -:comprising 2 a *pair iof 'levers 52 and 53 pivctallyconnected together at one end by a 1 pin :54 and connected at-"their:other =ends respectively to -th'e opposite ends of the brake band tl.*The hrake band is tightenedfiab'out the outer periphery or thehysteresis ring 25 by a solenoid *55 which tpulls 7 down on theirpivotall-y connected eniisrof the levers. :A' tension' sprlng EE isUsed in connecting one of :the' levers 5 3 to the brake bandin'ordertmgive-a smooth braking effort. In "this -:n1odification :ofthecmeehanism, the brake plug 38, the brake-drum 39,:.:anditheircooperating elements are replaced by the brake .bande Land "itsactuating linkage. -The solenoid 55 takes thezrplace of the solenoid- K5previously mentioned. The brake band 5i performs 'the function of thebrake plug 38, and otherwiseithe modifiedapparatusfunctions inithesamemanner as the apparatus described above withfreference to :"Figs.'l'to .4.

While solenoids have been described herein as the actuating means .forthe' hrake bands '45 and 51 'andifor the ring fl, any othe1' suitablemeans may 'be used for actuating these elements, su'ch' forexample asvacuum= devices opera-tedihy the vacuum of a gasoline 'engineintakemanifold. The operation oi'the mechanism as it maybe installedinan'automobile will best he understood by reference to the electricalcircuit diagram df Fig. "-7. The driving shaft 4 5 is eonnected to theengine and-"the driven zshaft 4'8 is connected to the -=drive wheelsthrough 'the usual universal joint, propeller shaft; differential gear,and: axles. A three-phase alternatore'i, driven thy the automobileengine, iselectrica'lly connectedtoia rectifier 5 3 designed-to deliverdirect current .r'electrio-energy o'f l'ow veltage (e. g.' 6-"7= volts)(one side of the rectifier is grounded, and its other (live) side isconnected-to 'one "contact cremattery-charger relay 59 and also-to onecontact ofahigh jgear relay 5'6. I'he-"other contact-of this'relayisconnecteol (through the brush' fi and slipiring23) "to theungrounded terminal'cif the coilsfiZZ .o'fthe hysteresis coupling.Further, thelive terminal of the rectifier is connected to theungroundedside of the actuating coil .:of a relayfil havingitslcontaet.arm loaded'by a spring -6:2 .which preventsthe relaycontactsffromclosinguntillthe alternator is rotating atsufiicientspeed to deliver the full-charging voltage required vto charge a storage rbattery t3. -When thisvoltage is adeve1oped,;the lcontactsloirrelayvt i close, thereby"connecting theua'ctuating coil of the charger rielaydie acrosstheibattery and effecting delivery or chargingacurrent'lto thethatteryfromfthe'rectifier athrough the acontacts .of the ichargerirelay. Thelbatteryflis connected "through abnormally closed hand'abralre;switchaied.to the:mo.ving:eontact farm :of a'selector switchhavingiforward(Fiaandzreverse GR) -'.m ntaetsv and: advantageously ELIS'OJKE neutralNi) :positicn. "The handrhrake switehifis.mountedrsoas to; bezopene'dwhen tthe hand .ubrake is set. ".tlhe .tselectorr switch :is26dvantageously mounted on the steering column adjacent the steeringwheel of the automobile. V

The forward (F) contact of the selector switch is connected to themovable arm of a low-high gear selector switch 66 which is normallybiased by a spring 61 into contact with the high gear (H) terminal ofthis switch. This (H) terminal of the low-high switch is connected tothe ungrounded terminal of the actuating coil of the high gear relay 6D.The low gear (L) terminal of the low-high switch is connected to oneside of the actuating coil of a low gear relay 68, the contacts of whichserve to open or close a circuit from the battery to ground through theactuating coil '69 of the low gear brake solenoid (45 in the apparatusof Figs. 1 to 4 or 55 in the apparatus of Figs. 5 and 6). The low-highgear selector switch 66 is advantageously located on the floorboard ofthe automobile in position where its movable arm can be shifted from itsnormal position in engagement with the high (H) terminal to engagementwith the low (L) terminal by a simple movement of the left foot of theautomobile driver.

The reverse (R) terminal of the selector switch 65 is connected to oneside of the actuating coil of a reverse gear relay 10, the contacts ofwhich serve to open or close a circuit from the battery to groundthrough the actuating coil H of the reverse gear brake solenoid 50. Thecircuit through the actuating coil of the reverse gear solenoid l0, andalso through the actuating coil of the low gear solenoid 68, iscompleted to ground through a normally open accelerator pedal switch 12mounted adjacent the accelerator pedal in such position that it remainsopen so long as no pressure is exerted by the drivers foot on theaccelerator pedal, but so that it is closed when the accelerator pedalis depressed beyond some very small initial movement.

In starting, the hand brake is on, keeping the hand brake switch 64open. Consequently the circuit to the selector switch 65 is open, andnone of the control relays 6B, 68 or can become energized. The enginenow may be warmed up by stepping on the accelerator pedal without givingeither forward or reverse motion to the automobile. The same may be doneif the selector switch is in the neutral (N) position even though thehand brake be released and the hand brake switch P 64 thereby be closed.

To start the automobile in the forward direc tion, the hand brake isreleased and the arm of the selector switch 65 is moved to make contactwith its forward (F) terminal. The automobile may now be started forwardin direct drive (high gear) by simply stepping on the accelerator pedal,for the high gear relay is now energized and the circuit between therectifier 58 and the coils 22 of the hysteresis coupling is completedthrough the high gear relay contacts. When the automobile engine isturning over only at idling speed, the voltage produced by thealternator 51 is so low as to be negligible, and the output of therectifier is correspondingly low. As the engine speed increases, thealternator (and rectifier) voltage output correspondingly increasesuntil at some minimum engine speed the alternator voltage attains itsfull rated value. This increase of alternator voltage with increasingengine speed is of advantage, for as the car starts and the engine speedincreases, the amount of current flowing through the coils of thehysteresis coupling increases with the alternator voltage, therebygradually increasing the strength of the electromagnetic coupling andleading to smoother acceleration than would result if maximum ornear-maximum voltage were impressed on the coils 22 at the moment ofstarting. Since the battery charger relay is open until the rectifiedalternator voltage has attained substantially its full value, thebattery voltage is not applied to the coils 22 during the initial periodof acceleration from engine idling speed.

To start in low gear, the selector switch 65 is moved to the forward (F)position and the highlow gear selector switch is actuated to place itsspring-loaded arm in contact with the low gear (L) terminal. Then, whenthe accelerator pedal is depressed and the switch I2 connected theretois closed, the low gear relay 68 is energized with resultingenergization of the low gear solenoid coil 69. This results in engagingeither the brake plug 38 with its drum 39 (in the apparatus of Figs. 1to 4) or the brake band 5| with the hysteresis ring 25 (in the apparatusof Figs. 5 and 6). At the same time the high gear relay is deenergized,so that the coils of the hysteresis coupling 22 are likewisede-energized. Hence the transmission operates in low gear in the manneralready described. The accelerator pedal switch 12 is included in thelow gear relay circuit so that the automobile can be stopped completelyin low gear by simply releasing the accelerator pedal without moving theselector switch 65 from the forward (F) position or releasing thehigh-low selector switch 66 from the low (L) position. In low gear, withthe brake plug 38 or the brake band 5| positively restraining thehysteresis ring 25 and forward sun gear 31 from rotation, the drivingand driven shafts are positively connected together. The acceleratorpedal switch permits releasing the brake on the hysteresis ringassembly, and so permits the engine to turn over at idling speed,without manipulating either the selector switch 65 or the high-lowselector switch 66.

To start the automobile in reverse gear, the arm of the selector switch65 is moved to the reverse (R) position. Then when the accelerator pedalis depressed enough to close the accelerator pedal switch 12, thereverse relay is energized, whereby the circuit through the coil H ofthe reverse gear solenoid 50 is completed. This results in tightening ofthe brake band 46 about the ring gear 3-6, so that the transmissionoperates in reverse gear as previously described. With the selectorswitch 65 in the reverse (R) position, neither the high gear relay 60nor the low gear relay 68 can be energized. The accelerator pedal switch12 functions in connection with the reverse gear relay 10 in the samemanner as it does in connection with the low gear relay 68 to permit theengine to turn over at idling speed without moving the selector switchfrom the reverse (R) position (for in reverse gear with the brake band46 restraining the ring gear 36 from rotation, the driving and drivenshafts of the transmission mechanism are positively connected together).

If pneumatic or vacuum control devices are used in place of thesolenoids 50 and herein described, the contacts of the relays 68 and 10are connected to electrically operated valves through which such devicesare themselves controlled; or if such valves are of a type that do notrequire a very high current to operate them, they may be connecteddirectly in place of the relays and the relays themselves may be omittedaltogether.

Although. the new transmission has been de.

part constituting a driven member; a drivin shaft connected to saiddriving member; an epi- 'cyclic gear train having two sun gears and aplanetary gear train, one of said sun gears being connected to saiddriving shaft and the other sun gear being connected to said drivenmember and the planetary gear train being connected to said drivenshaft, a rotatably mounted gear element operatively associated with saidplanetary gear train, braking means for said magnetic member, andbraking means for said gear element.

5. A device for drivingly connecting two rotatable members, comprisingtwo parts connected respectively to said members, one of said partscomprising an annular series of alternate north and south pole pieceseach having a pole shoe thereon extending circumferentially "beyond thepole piece all of which shoes have arcuate outer faces, the adjacentedges of each pair of adjacent pole shoes being closely adjacent andbeing separated by a gap which is only sufliciently large to preventhigh flux leakage, electrical means for energizing said pole pieces andshoes, said pole pieces, pole shoes and electrical means constituting adriving member; the second part comprising a ring of substantial massand bulk formed of magnetizable but unmagnetized high hysteresis lossmaterial the inner periphery of which surrounds and is positionedclosely adjacent the arcuate outer faces of the pole shoes and whichring forms the sole path for magnetic flux generated by said polepieces, said second part constituting a driven member; a driving shaftconnected to said driving member; an epicyclic gear train having two sungears and a planetary gear train, one of said sun gears being connectedto said driving shaft and the other sun gear being connected to saiddriven member; a carrier for said planetary gear train rotatably mountedon the driving shaft and connected to said driven shaft; a ring gearrotatably mounted on the driv- 'ing shaft and operatively connected tosaid planetary gear train; and means for holding said driven memberstationary and thereby establish a low gear ratio between said drivingand driven shafts, and means for holding said ring gear stationary andthereby reversing the direction in which said planetary gear carrierrotates said driven shaft.

6. A device for drivingly connecting two rotatable members, comprisingtwo parts connected respectively to said members, one of said partscomprising an annular series of alternate north and south pole pieceseach having a pole shoe thereon extending circumferentially beyond thepole piece all of which shoes have arcuate outer faces, theadjacentedges of each pair of adjacent pole shoes being closely adjacent andbeing separated by a gap which is only sufficiently large to preventhigh flux leakage, electrical means for energizing said pole pieces andshoes, said pole pieces, pole shoes and electrical means constituting adriving member; the second part comprising a ring of substantial massand bulk formed of magnetizable but unmagnetized high hysteresis lossmaterial the inner periphery of which surrounds and is positionedclosely adjacent the arcuate outer faces of the pole shoes and whichring forms the sole path for magnetic flux generated by said polepieces, said second part constituting a driven member; a driving shaftconnected to said driving member the foregoing constituting a slippablecoupling drive; an epicyclic gear train connecting the driven shaft tothe driving shaft, said epicyclic gear train comprising forward and rearsun gears and a planetary gear train engaging with both of said sungears, said rear sun gear being connected to the driving shaft and saidplanetary gear being connected to the driven shaft, said slippablecoupling device having two relatively rotatable members one of which isconnected to said driving shaft and the other of which is connected tosaid forward sun gear for altering the effective gear ratio of saidepicyclic gear train when the relative speeds of rotation of the membersof the coupling device are changed, and an auxiliary gear elementengaging with said epicyclic gear train for reversing the direction ofrotation of the driven shaft.

7. A device for drivingly connecting two rotatable members, comprisingtwo parts connected respectively to said members, one of said partscomprising an annular series of alternate north and south pole pieceseach having a pole shoe thereon extending circumferentially beyond thepole piece all of which shoes have arcuate outer faces, the adjacentedges of each pair of adjacent pole shoes being closely adjacent andbeing separated by a gap which is only sufliciently large to preventhigh flux leakage, electrical means for energizing said pole pieces andshoes, said pole pieces, pole shoes and electrical means constituting adriving member; the second part comprising a ring of substantial massand bulk formed of magnetizable but unmagnetized high hysteresis lossmaterial the inner periphery of which surrounds and is positionedclosely adjacent the arcuate outer faces of the pole shoes and whichring forms the sole path for magnetic flux generated by said polepieces, said second part constituting a driven member; a driving shaftconnected to said driving member; an epicyclic gear train connectingsaid driving shaft and said driven member to said driven shaft, havingtwo sun gears, one of the sun gears being connected to said drivingshaft and the other sun gear being connected to said driven member, thesun gears and planetary gears of the epicyclic gear train being arrangedso that said first member acts as a control member, providing largeamounts of torque to the driven shaft, while transmitting very littletorque between the driving and driven members of said first member.

8. A device for drivingly connecting two rotatable members, comprisingtwo parts connected respectively to said members, one of said partscomprising an annular series of alternate north and south pole pieceseach having a pole shoe thereon extending circumferentially beyond thepole piece all of which shoes have arcuate outer faces, the adjacentedges of each pair of adjacent pole shoes being closely adjacent andbeing separated by a gap which is only sufficiently large to preventhigh flux leakage, electrical means for energizing said pole pieces andshoes, said pole pieces, pole shoes and electrical means constituting adriving member; the second part comprising a ring of substantial massand bulk formed of magnetizable but unmagnetized high hysteresis lossmaterial the inner periphery of which surrounds and is positionedclosely adjacent the arcuate outer faces of the pole shoes and whichring forms the sole path for magnetic flux generated by said polepieces, said second part constituting a driven member; a driving shaftconnected to said driving member; an 'epicyclicgear train connectingsaid driving shaft andsaid 13 driven member to said driven shaft andmeans for providing said driven member with unidirectional rotarymotion, said gear train having two sun gears, one of said sun gearsbeing connected to said driving shaft, and the other being connected tosaid driven member, the sun gears and planetary gears of said epicyclicgear train being arranged to provide torque division between theepicyclic gear train and the driving and driven members of said firstmember.

ROBERT HELMER.

References Cited in the file of this patent UNITED STATES PATENTS NumberNumber Number Name Date Cofiee Feb. 14, 1905 Von Zweibergk June 17, 1919Murray Nov. 23, 1920 Charlton Mar. 1, 1927 Kibier Aug. 4, 1936 WintherJan. 22, 1952 Helmer July 15, 1952 FOREIGN PATENTS Country Date GreatBritain Apr. 2, 1935

